increased bleeding, if you are an anti-coagulants don't take it. ginseng, which many people take to make them feel better, may help, too. but, it may lower the blood sugar. so if you are diabetic, be careful. and, also, be careful with ginseng, if you are taking anti-depressants. and then, yohimbe, which comes from an african tree, may also help, but, the problem with yohimbe is some people with high blood pressure, it may elevate the pressure. zinc supplements also may help. but, avoid it in high doses, because, too much zinc can give you gastrointestinal side effects, and, other problems and those are the main supplements people use, they all help a little bit, but, be careful about their size effects, and you have to know when to use them, and be careful about taking other drugs with them.